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PubMed1996

NADPH diaphorase activity in peptidergic neurones of the parasitic nematode, Ascaris suum.

The histochemical marker for nitric oxide synthase, NADPH diaphorase, is known to co-localize in mammalian neurones with various classical neurotransmitters and neuropeptides. The nervous system of the parasitic nematode Ascaris suum has previously been shown to contain both NADPH diaphorase activity and neuropeptide immunoreactivity. This study examined the possibility that NADPH diaphorase and neuropeptide immunoreactivity may co-exist in the same neurones. Two antisera were used, one raised to KYSALMFamide, a C-terminal synthetic analogue of SALMFamide 1 (GFNSALMFamide), and another that recognizes calcitonin-gene-related peptide (CGRP). We provide evidence that in a distinct subset of neurones in the ventral, dorsal and lateral ganglia NADPH diaphorase staining and SALMFamide-like immunoreactivity are co-localized, suggesting a possible role for nitric oxide in modulating neuropeptide activity in these regions. CGRP-like immunoreactivity was less widely distributed, and was not consistently co-localized with NADPH diaphorase.

Animals↗
PubMed1996

NO nerves in a tapeworm. NADPH-diaphorase histochemistry in adult Hymenolepis diminuta.

The free radical nitric oxide (NO), which is synthesized by nitric oxide synthase (NOS), has recently been discovered to function as a neuronal messenger. The presence of NOS was detected in the nervous system of adult Hymenolepis diminuta with NADPH-diaphorase (NADPH-d) histochemistry. The NADPH-d histochemical reaction is regarded as a selective marker for NOS in neuronal tissue. NADPH-d staining was observed in nerve fibres in the main and minor nerve cords and the transverse ring commissures, and in cell bodies in the brain commissure, along the main nerve cords, in the suckers and the rostellar sac. NADPH-d staining was also observed in the wall of the internal seminal vesicle and the genital atrium. The pattern of NADPH-d staining was compared with that of the 5-HT immunoreactive nervous elements. The NADPH-d staining reaction and the 5-HT immunoreactivity occur in separate sets of neurons. This is the first time the NADPH-d reaction has been demonstrated in the nervous system of a flatworm, indicating that NOS is present and that NO can be produced at this level of evolution.

Animals↗
PubMed1997

Physiological effects of platyhelminth FMRF amide-related peptides (FaRPs) on the motility of the monogenean Diclidophora merlangi.

The actions of known platyhelminth FaRPs on the contractility of whole-worm preparations of the monogenean, Diclidophora merlangi have been examined in vitro for the first time. All of the peptides tested had excitatory effects on the motor activity of the worm. The order of potency for the peptides tested was: YIRFamide > GYIRFamide = RYIRFamide > GNFFRFamide = FLRFamide. However, although YIRFamide was more potent than GYIRFamide, the latter was the most efficacious on each of the motility parameters (tension, contraction amplitude and contraction frequency) examined at concentrations > or = 0.1 microM. Serotonin, which stimulates contractility in the worm was used as a positive control. The excitatory activity of turbellarian and cestode neuropeptides on a monogenean indicates at least some structural similarities in the neuropeptide receptors of these classes of flatworm.

Animals↗
PubMedDate not supplied

Evaluation of peptide libraries: an iterative strategy to analyze the reactivity of peptide mixtures with antibodies.

Peptide libraries corresponding to a presumed mixture of 50,625 tetrapeptides or 16,777,216 hexapeptides were each prepared in a single assembly by standard solid-phase peptide synthesis. By enzyme-linked immunosorbent assay, the tetrapeptide library was shown to inhibit the binding of an antiserum to FMRF amide with an FLRF capture antigen; the hexapeptide library was shown to inhibit the binding of a monoclonal antibody to a 28 amino acid peptide with the corresponding peptide capture antigen. An iterative strategy of variation was used to determine for each position in the tetra- or hexapeptides which amino acid contributed the most to activity. As a result we were able to logically select out of the tetrapeptide library the sequence FLRF and to select out of the hexapeptide library a sequence that differed from the apparent probable epitope but was twice as active. A single amino acid substitution in the logically derived sequence gave a peptide that was 35 times as active as the hexapeptide sequence in the original 28 amino acid peptide.

Amino Acid Sequence↗
PubMedDate not supplied

Localization of putative neurotransmitters in the mantle and siphuncle of the mollusc Nautilus pompilius L. (Cephalopoda).

The neurotransmitter supply in the nerve endings of the mantle and the siphuncle, i.e. in organs that are responsible for the shell formation in the ectocholeate Nautilus pompilius, were investigated with electron microscopical, fluorescence-, immuno- and enzyme histochemical methods as well as with high pressure liquid chromatography (HPLC). Using antibodies against serotonin and the tetrapeptide FMRF-amide, positive reactions were demonstrated immunohistochemically within the terminal nerve fibres of the mantle and the vessels of the siphuncle. Enzyme histochemical proof of the presence of specific acetylcholinesterase yielded positive results in the muscle fibres of the mantle and siphuncle. Additionally, in the mantle, glyoxylic acid-induced fluorescence was shown within the nerve endings indicating catecholamines as neurotransmitters, whereas in the siphuncle such fluorescence did not appear. However, the HPLC-analyses showed that in the mantle and also in the siphuncle the content of dopamine is higher than that of noradrenaline whereas only traces of adrenaline occur in both organs suggesting dopamine as a putative neurotransmitter. Transmission electron microscopical examination of the nerve endings of both organs revealed that different types of vesicles were distinguished that could be considered as cholinergic, aminergic and peptidergic structures.

Acetylcholinesterase↗
PubMed1997

Neuropeptide-containing nerve fibres in the human parotid gland: a semiquantitative analysis using an antibody against protein gene product 9.5.

The occurrence and distribution of neuropeptide-containing fibres in the human parotid gland were examined by the peroxidase-antiperoxidase method with attention to the quality of fixation and the condition of patients. Many fibres immunoreactive for neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) and a moderate number of galanin-positive (GAL) fibres were distributed around the acini. A moderate number of NPY and VIP fibres were distributed around the intercalated ducts. The semiquantitative mean densities (+/- SD) of periacinar NPY, VIP and GAL fibres expressed as a percentage of the total protein gene product (PGP) 9.5 immunoreactive fibres were 75.62 +/- 7.25%, 70.52 +/- 9.33% and 41.76 +/- 5.45%, respectively, whereas those of substance P (SP), calcitonin gene-related peptide (CGRP) and FMRF amide (FMRF) fibres were below 10%. The mean densities of NPY and VIP fibres around the intercalated ducts expressed as the percentage of PGP 9.5 fibres associated with these ducts were 52.37 +/- 6.19% and 59.62 +/- 7.02% respectively. Those of SP, CGRP, GAL, and FMRF fibres were below 10%. The densities of NPY, VIP, SP, CGRP, GAL and FMRF fibres around the striated and excretory ducts were also below 10%. In the vasculature, NPY fibres were the most prominent. Similarly, the mean density of perivascular NPY fibres was 93.76 +/- 2.03%. No somatostatin or leucine or methionine enkephalin immunoreactivity was detected around the acini, duct system or blood vessels. These findings suggest that, in this gland, the periacinar NPY, VIP and GAL fibres may participate in regulating the synthesis of saliva and its secretion and that perivascular peptidergic fibres, especially NPY fibres, may be involved in controlling local blood flow.

Adult↗
PubMed1989

A neuromodulator of synaptic transmission acts on the secretory apparatus as well as on ion channels.

The mechanisms that underlie synaptic plasticity have been largely inferred from electrophysiological studies performed at sites remote from synaptic terminals. Thus the mechanisms involved in plasticity at the secretory sites have remained ill-defined. We have now used somatic synapses of cultured Helisoma neurones to directly assess presynaptic ion conductances and study the secretory apparatus. At these synapses we determined the actions of a modulatory neuropeptide, Phe-Met-Arg-Phe-NH2 (FMRFa), on the release of the neurotransmitter acetylcholine (ACh). Using voltage- and calcium-clamp techniques, we have demonstrated that FMRFa causes a presynaptic inhibition of ACh release by (1) reducing the magnitude of the voltage-dependent calcium current, and (2) regulating the secretory apparatus. The photolabile calcium cage, nitr-5 (refs 3-8), was dialysed into the presynaptic cell. In response to ultraviolet light, calcium was released from nitr-5 and ACh secretion was stimulated. Under conditions of constant internal calcium, FMRFa reduced the rate of ACh release. Thus we conclude that FMRFa reduces the influx of calcium during the action potential and decreases the sensitivity of the secretory apparatus to elevated internal calcium, thereby contributing to a presynaptic inhibition of transmitter release.

Acetylcholine↗
PubMed1990

Peripheral organs control central neurogenesis in the leech.

Interactions between developing nerve centres and peripheral targets are known to affect neuronal survival and thus regulate the adult number of neurons in many systems. Here we provide evidence that peripheral tissues can also influence cell numbers by stimulating the production of neurons. In the leech Hirudo medicinalis, there is a population of several hundred neurons that is found only in the two segmental ganglia that innervate the genitalia and which seem to be added gradually during post-embryonic maturation. By monitoring 5-bromo-2'-deoxyuridine incorporation immunohistochemically, we have now determined that these neurons are actually born late in embryogenesis, well after all other central neurons are born and after efferent and afferent projections are established between these ganglia and the periphery. Ablation of the male genitalia early in embryogenesis, or evulsion of the nerves that connect them to the ganglia, prevent the birth of these neurons. However, they fail to appear ectopically when male genitalia are transplanted to other segments, despite innervation by local ganglia. We conclude that the generation of the late-appearing neurons depends on a highly localized signal produced by the male genitalia, to which only the ganglia that normally innervate these organs have the capacity to respond.

Animals↗
PubMed1992

Identification and characterization of aminopeptidases from Aplysia californica.

Aminopeptidase activities were identified in extracts of kidney, ovotestis, head ganglia, heart and haemolymph of Aplysia californica. These enzyme preparations hydrolysed [3H][Leu]enkephalin at the Try-1-Gly-2 bond as determined by h.p.l.c. analysis of cleavage products. In all these tissues, enkephalin-degrading aminopeptidase activities were present both in membrane-bound and cytosolic fractions. The bivalent-cation-chelating agent, 1,10-phenanthroline, inhibited kidney membrane aminopeptidase activity with an IC50 of 30 microM, suggesting that this enzyme is a metalloproteinase. The aminopeptidase inhibitor amastatin was the most potent inhibitor of [Leu]enkephalin degradation (IC50 25 nM) by membrane-bound aminopeptidase, and bacitracin, bestatin and puromycin were about 100-1000 times less potent. In contrast with membrane-bound aminopeptidase, the cytosolic form is sensitive to puromycin. Angiotensin-converting enzyme inhibitor had no effect on [Leu]enkephalin degradation by kidney membranes, while the neutral endopeptidase inhibitors were poor inhibitors of the enzymes in this preparation. The Km values of the aminopeptidase in the kidney membranes and cytosolic fractions for the [Leu]enkephalin substrate were 2.4 and 7.4 microM respectively. The aminopeptidase present in the kidney membranes also hydrolysed endogenous Phe-Met-Arg-Phe-amide peptide at the Phe-1-Met-2 bond as well as synthetic alanine p-nitroanilide and leucine p-nitroanilide. When used in a competition assay, these substrates inhibited hydrolysis of [3H][Leu]enkephalin, suggesting that the same enzyme degraded all these substrates. Taken together, these results suggest that Aplysia tissues contain both a membrane-bound aminopeptidase related to the mammalian aminopeptidase N and a cytosolic puromycin-sensitive aminopeptidase.

Aminopeptidases↗
PubMed2003

Modulation of spontaneous and evoked EPSCs and IPSCs in optic lobe neurons of cuttlefish Sepia officinalis by the neuropeptide FMRF-amide.

The effects of the neuropeptide FMRFa on spontaneous excitatory postsynaptic currents (sEPSCs) and inhibitory postsynaptic currents (sIPSCs), as well as on evoked EPSCs and IPSCs, in two types of neurons within the central optic lobe of cuttlefish were examined using the whole-cell voltage-clamp technique. FMRFa (1-10 micro m) did not affect cell membrane resting potentials, but reversibly reduced both the frequency and amplitude of sEPSCs in neurons within the medulla region of the optic lobe while increasing the frequency and amplitude of their sIPSCs. For centrifugal neurons in the inner granule cell layer of the optic lobe, FMRFa (1-10 micro m) decreased both the frequency and amplitude of sEPSCs. In the presence of tetrodotoxin (0.5 micro m), neither the interevent interval, nor amplitude distributions of the miniature EPSCs or the miniature IPSCs, were affected by FMRFa, implying a presynaptic action of FMRFa on the optic lobe neurons. Bath application of the neuropeptide also abolished or reduced in amplitude the evoked EPSCs and increased the amplitude of evoked IPSCs in optic lobe neurons, showing that FMRFa induced similar effects on evoked as on spontaneous postsynaptic currents. These results demonstrate the complex range of modulatory effects FMRFa can have within central nervous system circuits.

Animals↗
PubMed1984

Inhibition of spontaneous and opiate-modified nociception by an endogenous neuropeptide with Phe-Met-Arg-Phe-NH2-like immunoreactivity.

In rats the antinociceptive actions of morphine (injected intraventricularly) or of [Met5]enkephalin-Arg6-Phe7 (YGGFMRF) (injected intrathecally) were attenuated by a pretreatment with 10 microliter of artificial cerebral spinal fluid containing 1 microM captopril/1 microM bestatin/2.5 microM Phe-Met-Arg-Phe-NH2 (FMRF-NH2) given 5 min earlier by the same route. A high molecular weight form of FMRF-NH2 purified from bovine brain attenuated the antinociceptive action of YGGFMRF. IgG, prepared from a specific FMRF-NH2 antiserum, elicited a moderate antinociception reversible by naloxone; in contrast, IgG prepared from control serum failed to change tail-flick latencies. In rats receiving morphine every 2 hr and anti-FMRF-NH2 IgG every 4 hr, the antinociceptive action was still evident after eight successive injections; in rats receiving only morphine, the antinociceptive action had disappeared after six successive injections. Morphine (1 microM) added to the perfusion fluid of the subarachnoidal spaces of rat spinal cord releases FMRF-NH2-like peptides in the perfusate.

Animals↗
PubMed1984

The goldfish nervus terminalis: a luteinizing hormone-releasing hormone and molluscan cardioexcitatory peptide immunoreactive olfactoretinal pathway.

Antisera to two putative neurotransmitters, luteinizing hormone-releasing hormone (LHRH) and molluscan cardioexcitatory tetrapeptide (H-Phe-Met-Arg-Phe-NH2; FMRF-amide), bind specifically to neurites in the inner nuclear and inner plexiform layers of the goldfish retina. Retrograde labeling showed that intraocular axon terminals originate from the nervus terminalis, whose cell bodies are located in the olfactory nerves. Double immunocytochemical and retrograde labeling showed that some terminalis neurons project to the retina; others may project only within the brain. All terminalis neurons having proven retinal projections were both LHRH- and FMRF-amide-immunoreactive. The activity of retinal ganglion cells was recorded with microelectrodes in isolated superfused goldfish retinas. In ON- and OFF-center double-color-opponent cells, micromolar FMRF-amide and salmon brain gonadotropin-releasing factor ( [Trp7, Leu8] LHRH) caused increased spontaneous activity in the dark, loss of light-induced inhibition, and increased incidence of light-entrained pulsatile response. The nervus terminalis is therefore a putatively peptidergic retinopetal projection. Sex-related olfactory stimuli may act through it, thereby modulating the output of ganglion cells responsive to color contrast.

Animals↗
PubMed1987

Tail shock produces inhibition as well as sensitization of the siphon-withdrawal reflex of Aplysia: possible behavioral role for presynaptic inhibition mediated by the peptide Phe-Met-Arg-Phe-NH2.

Recent studies have shown that, in addition to being modulated by presynaptic facilitation, the sensory neurons of the gill- and siphon-withdrawal reflex of Aplysia are also capable of being modulated by transient presynaptic inhibition produced by the peptide Phe-Met-Arg-Phe-NH2. These two modulatory effects involve different second-messenger systems: the facilitation is mediated through cAMP-dependent protein phosphorylation, and the inhibition is mediated through the lipoxygenase pathway of arachidonic acid. To explore the behavioral function of this inhibition, we have carried out a parametric analysis of the effect of tail shock on the siphon-withdrawal reflex. In addition to producing sensitization of the withdrawal reflex, tail shock also transiently inhibits the reflex. The inhibition is produced by relatively weak shock, whereas sensitization is more prominent and may mask the inhibition with stronger shock. Furthermore, inhibition is not observed after habituation training. Cellular studies suggest that the behavioral inhibition is mediated, at least in part, by presynaptic inhibition of transmitter release from the siphon sensory neurons. Moreover, we have identified an interneuron within the left pleural ganglion (LPL16) that shows Phe-Met-Arg-Phe-NH2 immunoreactivity, is activated by tail shock, and simulates the presynaptic inhibitory actions produced by tail shock. Therefore, our results suggest that presynaptic inhibition mediated by Phe-Met-Arg-Phe-NH2 and its lipoxygenase second messenger contributes to behavioral inhibition of the siphon-withdrawal reflex.

Action Potentials↗
PubMed1988

Role of two different guanine nucleotide-binding proteins in the antagonistic modulation of the S-type K+ channel by cAMP and arachidonic acid metabolites in Aplysia sensory neurons.

The role of guanine nucleotide-binding proteins (G proteins) in the cAMP-dependent action of serotonin (5-HT) and the antagonistic action of the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRF-amide), mediated by the lipoxygenase metabolites of arachidonic acid, was investigated in Aplysia sensory neurons. Intracellular injection of guanosine 5'-[gamma-thio]triphosphate (GTP[gamma-S]) mimics the hyperpolarizing action of FMRF-amide due to activation of the S K+ current and alters the transient response to FMRF-amide into an irreversible (or only partially reversible) response. At higher concentrations, GTP[gamma-S] occludes the response to FMRF-amide. Injection of activated pertussis toxin inhibits the response to FMRF-amide but not to 5-HT. Injection of guanosine 5'-[beta-thio]diphosphate inhibits the response to FMRF-amide by approximately equal to 50% and completely blocks the response to 5-HT. Three lines of evidence suggest that the FMRF-amide-activated G protein is involved at an early stage of the arachidonic acid cascade, prior to the release of arachidonate. (i) Pertussis toxin injection blocks the hyperpolarizing response to FMRF-amide but not to exogenously applied arachidonic acid. (ii) Two blockers of the arachidonic acid cascade inhibit the hyperpolarizing responses to both FMRF-amide and GTP[gamma-S] (and unmask a 5-HT-like depolarizing response to the nucleotide). (iii) Concentrations of GTP[gamma-S] that alter the kinetics of the FMRF-amide response have no effect on the hyperpolarizing response to arachidonic acid. We conclude that a pertussis toxin-sensitive G protein most likely acts to couple the FMRF-amide receptor to phospholipase activation and arachidonic acid release, whereas a pertussis toxin-insensitive G protein couples the 5-HT receptor to adenylate cyclase.

Animals↗
PubMed1995

Mutually exclusive neuronal expression of peptides encoded by the FMRFa gene underlies a differential control of copulation in Lymnaea.

An innovative method, direct peptide profiling of small samples of nervous tissue by matrix-assisted laser desorption ionization mass spectrometry, in combination with peptide characterization, immunocytochemistry in conjunction with specific neuronal labeling by backfilling of the penis nerve, and bioassay of peptides was used to study the intrinsic neuronal expression patterns of distinct sets of related FMRFa peptides and their significance for the organization of male copulation behavior in the mollusk, Lymnaea stagnalis. Previous studies indicate that the sets of FMRFa-related and GDPFLRFa-related peptides are encoded by two alternatively spliced transcripts of the single FMRFa gene. Direct mass spectrometry revealed that both FMRFa-related and GDPFLRFa-related peptides are present in the penis nerve, the sole nerve that innervates the penis complex. Accordingly, authentic FMRFa, GDPFLRFa, and related peptides were purified from the penis complex. The loci of synthesis of FMRFa and related peptides could be traced to the right cerebral ventral lobe, those of GDPFLRFa and related peptides to the B group neurons in the right parietal ganglion and to a few unidentified neurons in the right pleural ganglion. Notwithstanding their related structures, the two sets of peptides have distinctly different actions on the penis retractor muscle.

Alternative Splicing↗